The present invention relates to pressure sensors. More specifically, the invention relates to pressure sensors which are used in a corrosive environment.
Pressure sensors are used to measure the pressure process fluids used in industrial processes. The measured pressure is used to monitor and/or control operation of the industrial process.
The process fluid which is sensed by the pressure sensor may, in some instances, be corrosive or otherwise require a highly pure environment. One technique to address such installation requirements is to separate the pressure sensor from the process fluid using an isolation diaphragm. An oil fill couples the pressure sensor to the isolation diaphragm such that pressure applied to the diaphragm is applied to the pressure sensor. However, this isolation technique can introduce errors in pressure measurements.
Various pressure sensor designs are known in the art. One type of pressure sensor is formed of an elongate substantially brittle material. The sensor itself can be fabricated of a corrosion resistance material such as sapphire. Examples of this type of pressure sensor are shown and described in U.S. Pat. No. 5,637,802, issued Jun. 10, 1997; U.S. Pat. No. 6,079,276, issued Jun. 27, 2000; U.S. Pat. No. 6,082,199, issued Jul. 4, 2000; U.S. Pat. No. 6,089,097, issued Jul. 18, 2000; U.S. Ser. No. 09/478,434, filed Jan. 6, 2000; U.S. Ser. No. 09/478,383, filed Jan. 6, 2000; U.S. Ser. No. 09/477,689, filed Jan. 6, 2000; U.S. Ser. No. 09/603,640, filed Jun. 26, 2000; U.S. Ser. No. 09/755,346, filed Jan. 5, 2001; and U.S. Ser. No. 09/978,311, filed Oct. 15, 2001 which are incorporated herein by reference in their entirety.
However, in some embodiment, the bond or seal which is used to couple the elongate pressure sensor to the mounting structure can be corroded by certain types of process fluid or can be a source of contaminates to highly pure process fluids.